Answer: I wouldn't do anything other than leave the cactus in a brightly lit room. If you packed it in a box for the trip home, the temperature may have been too warm inside the vehicle, or too cold in the trunk to suit the plant. Or, a heat vent could have concentrated hot air on the plant. In any event, it should recover. Don't water for 3-4 weeks. This will force new root growth (as the plant seeks moisture) which should strengthen the root system. Your cactus won't require a great deal of water during the winter months but should be watered sparingly every 15-20 days during the spring and summer months.
Best wishes with your prickly pear.
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